kernel - Fix pmap_remove() issue.

kernel - Fix pmap_remove() issue.

* When the inner loop of pmap_remove() broke out due to pmap_remove_pte()
  blocking it 'jumped' the sindex to pdnxt, thus any remaining pages in
  that page table page would get skipped.

* pmap_remove_pte() and friends used to return non-zero if they 'blocked'.
  Unfortunately they could actually block whether they returned 0 or non-zero,
  causing the problem.  Remove the check entirely.

* Adjust misc functions which we no longer need the return value for.

* I don't know if this had anything to do with the wire_count panic.
  The failure mode should have been caught by numerous other assertions
  in the code but wasn't.  get_ptbase() relies on a test of pmap->pm_cached
  to determine if a page directory page mapping changes so it should not
  have been possible for it to continue the loop and access a stale ptep.

  If it were possible it might account for a wire_count panic later on but
  it doesn't seem like it should be possible.